Stretch press jaw



July 5, 1960 R. A. MYERS STRETCH PRESS JAW Filed Jan. 28, 1952 I1g L- INVENTOR. lQ/Gf/AZJ ,4. Myies United States 2,943,862 STRETCH PRESS JAW Richard A. Myers, Los Angeles, "Calif., assignor to Douglas Aircraft Company, Inc, Santa Monica, Calif.

Filed Jan. 28, 1952, Ser. No. 268,650

Claims. (Cl. 2794) Thisinvention relates to a jaw for gripping a workpiece and more particularly to a jaw adapted to grip a workpiece having any one of a variety of cross-sectional shapes and yet, with only minor changes, readily capable of efiiciently gripping other work-pieces having other cross-sectional shapes.

In carrying out various forming or quality improving operations, particularly where metals are being shaped,

heat treated or cold worked, it is necessary that a portion of the metal or other material be gripped or otherwise held against movement. For example, where it is necessary to stretch, machine, bend or otherwise alter the shape or size of an elongate metal member, it is common practice to grip either one or both ends of the member by means of jaws or vises.

The prevalent practice is to form the opposed sections of the jaw from a hard metal which is cast or machined to correspond with the surface configuration of the member or work-piece to be held. The jaws are actuated by a collet, screw, or linkage arrangement in order to force them generally radially into compressive contact with the end portion of the work-piece. When it is necessary to carry out the same forming operation on a similar work-piece having another crosssectional outline, it is likewise necessary to obtain another set of jaws of corresponding shape. This means a heavy investment of time and money in complete sets of jaws of varying gripping surface shapes in order for a concern to be able to process work-pieces conforming to the numerous standard cross-sectional shapes as well as various special shapes.

The present invention solves this difficult problem by taking a completely different and novel approach to it. The jaw of the present invention comprises a vessel or housing containing a plurality of hard bodies such as sand blasted steel bflls which serve as the gripping means. The housing has a piston or movable wall portion mounted in it which may be hydraulically or mechanically actuated to force the steel balls into one end of the housing.

To permit the end of the workpiece to be inserted into the housing and into contact with the steel balls a removable retainer plate is mounted on and forms a part of the housing. The work-piece is passed through a guide slot conforming to its cross-sectional shape which is formed in the retainer plate. When pressure is applied to reduce the volume of the space containing the steel balls they are forced to move or flow relative to each other and relative to the work-piece to thereby surround and compressively contact the work-piece regardless of its cross-sectional shape.

Thus, when it is desired to grip a workpiece of a different shape the operator simply removes the retainer plate and selects another having the correct guide slot shape and inserts it in the jaw. The retainer plate is of course relatively inexpensive and a complete set for use withthe jaw of the present invention would represent only a fraction of the investment required where a completeset of jaw shapes and sizes is needed, in accordance with the presently prevalent practices.

2,943,862 Patented July 5, 1960 Other features and advantages of the present invention will be apparent from the following description taken in connection with the accompanying drawing in which:

Figure l is a fragmentary perspective view illustrating one form of the jaw and showing in dotted lines the position of the work-piece and retainer plate when a work piece is about to be gripped so that a forming operation can be carried out.

Figure 2 is a fragmentary side elevation depicting the jaw'in operation and illustrating in dotted lines the position to which one embodiment of the jaw may be rotated when it is desired to remove the work-piece.

Referring now to Figure 1, a chamber is formed by the housing or vessel 10 and is divided into two spaces or sections 12 and 14 by a wall 16. The rear end 18 of the housing is formed with an internally threaded hub 20 which serves to connect the housing to a shaft or other connection 22 extending from a stretch press or other metal working unit not shown. 7

The wall or partition 16 of the present embodiment contains a bearing unit 24 which is adapted to receive a piston rod or shaft 26 which is mounted in the bearing unit for movement in the direction of its longitudinal axis. An actuating piston 28 is secured to one end of the piston rod and is adapted to move with the rod. 'An

actuated or squeezing piston 30 is mounted on the opposite or forward end of the piston rod which extends into the forward space 12 of the divided vessel and serves as a means for reducing the working volume of that space.

Hydraulic fluid lines 32 and 34 connect the fluid ports 36 and 38 of the housing 10 to an hydraulic system not shown. Thus, when fluid is pumped into port 38 the fluid pressure will move the actuating piston 28, the piston rod 26 and the actuated piston 30 toward the forward or front end 40 of the housing; that is, to the left as seen in Figure 2. This action will reduce the 'volume of the forward space .12; and gripping means 42 to firmly grasp the work-piece or member 44- as will be subsequently described in greater detail. The gripping means may be steel balls or the like, of the same or variegated sizes, and preferably are sand blasted or otherwise roughened. To release the work-piece, the fluid flow is reversed to pump fluid into port 36 to act on the outer side of the piston 28. Pistons 28 and 30 then move to the right, increasing the working volume and freeing the balls 42 so that they no longer grip the work-piece.

The forward end 40 of the housing 10 is closed by retention means here shown as a retainer plate 46 which is removable and interchangeable with other similar plates. The plate thus forms one wall of the housing and is adapted to slide in grooves 48 cut in mounting brackets or seats 50 which are bolted or otherwise connected to and made a part of the housing. A stop in the form of a pin 51 is used to locate the retainer plate centrally. As shown best in Figure 1, a guiding entrance or passage in the form of a slot or groove 52 is formed in the retainer plate and serves to permit the guided entry of the workpiece into the forward space 12 occupied by the steel balls or other gripping means 42. The guiding entrance, of course, must take the same general cross-sectional shape as the member to be formed; However, it need not be ,a snug fit, since the gripping bodies 42 cannot escape between the slot surface and the work-piece 44.

In order to prevent spillage of the balls 42 when the retainer plate 46 is removed for replacement by another plate having a guide slot of a different shape a second set of grooves 54 is formed in the brackets 50 and is adapted to receive a temporary retaining shim 53 in a manner similar to the insertion of the retainer plate. This shim is preferably made of thin sheet metal and is inserted prior to removal of the retainer plate. Then the latter can be removed and a second plate inserted having the desired form of guiding entrance for the particular membe: next to be gripped. It has also been found that spillage tion up to vertical. In this-position spillage can be avoided during the removal of the retainerimeans 4d. This arrangement' alsohas the advantage'of avoidmgsprllage during and after removal of the Work-piece when the size of the slot in plate 46 is such that the gripping balls can pass through it. This latter result is likewise achieved simply by upwardly rotating the housing prior tothe time that the Work-piece is withdrawn.j

Thehousing then should be retained inrthis position until such time as a new work-piece'is inserted.

'The gripping means 42 maybe composed of a plurality of steel balls, tumbling stars, or any type of pebble or or piston30 is actuated to reduce thevolume of the space 12 which theyoccupy. By choosing bodies which will move relative to each other under pressureand by using them to directly grip the work-piece instead of jaws of the present invention can b e used to 'grip sheet mum volume of the forward space should not be com- 7 pletely filled with the steel balls. By leaving some space 7 would follow a simple straight line. a

material by simply widening the forward space, housing and retainer plate to enable them to receive sheet sizes of the width contemplated. In such a case the slot52 In most instances it has been found that the maxito be taken up by the movement of the piston the balls are shifted sufficiently before much force is applied to assure the operator'that all space around the end of the work-pieceis contacted by the steel balls.

Although the now preferred embodiments of the present 5 invention have been illustrated and described it is to be ovalshaped :hard bodies which willmove relative to a 7 h 0th r and to the insertedwork iece when the wall V e p -wall; first and second p ston means mounted on ,the-

opposite ends of said rod in said respective 'first and" V merely serving to actuate vise type jaws it is apparent that various" types of cross sections can be handled. Figures 1 and 2. show the jaw in use to'grip aT-shaped section. However, it is obvious that V, L, U, H, I and numerous other common cross sections can be easily and firmly gripped. In production use it has been found that the gripping action is such that the work-piece itself will fail beforeany slippage under high loading will occur. This has very definitely notbeen true of the cast or machined steel or Kirks'ite typeof jaw which has been previously used.

. In the preferred form amixture of generally spherical steelballs ranging from to /s of an inch in diameter have been found to be most successful. *However the size :and type of ball or body used depends primarily upon understood that the invention need not be limited thereto for it is susceptible to changes in form; detail andapplication within the scope of the I claim:

appended claims.

1. A stretch press jaw for gripping an elongate member, comprising: a space enclosing vessel; .a wall mounted in the interiorofsaid vessel and dividing the space enclosed into first and second sections; a piston rodpassing through and longitudinally movable in relationtosaid' second sections; means for transmitting hydraulic pres-r' sure to one of said divided sections in a mannerwhich' will actuate the first piston means mounted therein to thereby actuate the second piston means mounted-on the opposite end of said piston rod; retainer means closing the end of said vessel adjacent the space containing said second piston means; guide means formed in said retainer means conforming substantially to theQcross-sectional outline of one end ofsaid elongate member to tion of the space defined by said retainer means, the

permit passage of said end through said retainer means and into the adjacent section of said vesesel; and a multi:

plicity of discrete hard bodies filling a substantial pora second piston means and said vessel; said hard bodies being movable with respect to each other and to the end of said member when said first and second piston means the size of the jaw and the general type of work which the user intends to accomplish; If members ranging primarily in the smaller cross-sectional areas are to .be'

. handled, smaller diameters might be used to greater advantage. With Work-pieces generally falling in the heavier more bulky categories larger "bodieswould suflice and would aid in avoiding any spillage. It has also been found that the balls should have a sand blasted or other- .wise roughened surface since this-improves their gripping characteristics.

The forward space 12 defined by the piston QO housing 1'0 and retaining plate 46 is shown'herein the form of a truncated cone since it has been found that this shape permits of the maximum gripping action. It is readily apparent that numerous housing shapes may be employed ranging from. cubical to spherical. The major requisite is that some means such as a piston 30 or movable Wall be provided to decrease the volume and thereby apply pressure-to the work-piece by way o f the steel balls. Hydraul'ic actuation of the piston is most convenient. However, mechanical actuation by screws or springs is also feasible. Any of these arrangements will achieve the basic ad vantages ofthe invention since the steel balls are permittedto act as if it were a fluid. By permitting the balls to act directly upon the Work piece, instead-of merely using them to operate vise or similar type jaws, unusual flexito grip almost any configuration This also eliminates the problems, present where vise typejaws are used to grip a surface having an irregularity or flaw which precents surface to surface contact. The steelballs simply I each other and into gripping contact with the end of said bility is achieved sinceae balls readily adapt themselves V are actuated to thereby be forced into intimate contact with each other and into gripping contact withjthe end 7 of said member. v

2. A jaw for use on a stretch press for. gripping an elongate member, comprising: a cylinder having an in 'terior Wall defining in one end a truncated cone surface;

piston means mounted in said cylinder and movable .to-

ward the interior thereof to reduce the 'volumerof the interior of said cylinder; means for actuating said piston means; a removable retainer plate closing the end of said cylinderopposite said piston means; guide meansformed in said retainer plate conforming substantially to the crosshard bodies being movable with respect to each other and to the end of said member when said piston means is' actuated to thereby be forced into intimate contact with member; and pivotal supporting means'whereby said jaw' may be rotated upwardly from itsroperating position to thereby enable the operator to avoid spillage of said-hard bodies out of said guide means during insertion'and removal ofrsaid elongate member. 7

3; A chuck jaw for gripping an elongate member to be subjected to a load, comprising: means forming a chainber; force-applying means forming a wall ofjsaid chain her and movable toward the interior thereof :to reduce the volume of said chamber; readily removable-retainer means forming another wall ofsaidcham'ber said retainer means including means forming an opening therein to provide a guiding entrance for insertion ot a portion of said elongate member into the interior of said chamber; a multiplicity of hard generally spherical bodies, said bodies substantially filling said chamber and being disposed therein in unrestrained relation to each other and said elongate member, said bodies being adapted to be crowded into intimate contact with each other and into gripping contact with said elongate member when said force-applying means is moved to reduce the volume of said chamber; closing means; and receiving means formed in a wall of said chamber adjacent said retaining means, said receiving means being adapted to receive said closing means in a manner which prevents any of said bodies from spilling out of said chamber through said opening in said retainer means.

4. In a metal forming machine of the :type in which the opposite ends of a metal work-piece are clamped in order to subject it to a forming operation, a work-piece gripping device comprising the combination of: a container provided with means forming an opening therein to form a guiding entrance for insertion of a portion of a work-piece into the interior of said container; forceapplying means forming a portion of said container and movable toward the interior thereof to reduce the volume of said interior; a multiplicity of hard bodies freely disposed in and substantially filling said container, the configurations and free disposition of said bodies in said container adapting same for movement relative to each other and to the work-piece in response to movement of said force-applying means toward the interior of said container to thereby be crowded into intimate contact with each other and into gripping contact with said work-piece; and pivot means pivotally mounting said gripping device to permit said device to be rotated upwardly from its operating position to thereby avoid spillage of said hard bodies out of said guiding entrance during insertion and removal of said work-piece.

5. In a device for gripping a workpiece, a container having an open end, a readily removable retainer closing said open end, guide means on said container to hold said retainer in longitudinal relation to said container having projections overlying opposite edges of said retainer so that said retainer is movable laterally in said guide means, a workpiece shape conforming aperture in said retainer to admit a portion of said workpiece into said container, a multiplicity of hard particulate bodies filling said container and freely movable therein, and means for reducing the volume of said container to crowd said bodies into contact with each other and with said retainer and into gripping contact with said workpiece.

6. In a device for gripping a workpiece, a container having an open end, a readily removable retainer closing said open end, means on said container having projections overlying opposite portions of said retainer to hold said retainer in longitudinal relation to and spaced from said container a distance sufiicient to slidingly receive a coverplate between said retainer and said container, a workpiece shape conforming aperture in said retainer to admit a portion of said workpiece into said container, a multiplicity of hard particulate bodies partially filling said container and freely movable therein, and means for reducing the volume of said container to crowd said bodies into contact with each other and with said retainer and into gripping contact with said workpiece.

7. In a device for gripping a workpiece, a container having an open end, a readily removable retainer closing said open end, means on said container having projections overlying opposite edges of said retainer to hold said retainer in longitudinal relation to and spaced from said container a distance suflicient to slidingly receive a coverplate between said retainer and said container, matching recesses in the opposing faces of said holding means to hold said coverplate in longitudinal relation to said container, a workpiece shape conforming aperture in said retainer to admit a portion of said workpiece into said container, a multiplicity of hard particulate bodies partially filling said container and freely movable therein, and means for reducing the volume of said container to crowd said bodies into contact with each other and with said retainer and into gripping contact with said workpiece.

8. A jaw for gripping a work piece comprising: a vessel; means for mounting said vessel; piston means forming a portion of the wall of said vessel and adapted to enter the interior of said vessel to thereby decrease its volume; means for actuating said piston means; removable retainer means forming another portion of the wall of said vessel; guide means formed in said retainer means to permit a confined entry of aportion of said work piece into said vessel; and a plurality of hard particulate gripping bodies of varied sizes contained within said chamber; said bodies being movable with respect to each other and to said work piece when said piston means is actuated to thereby be forced into intimate contact with each other and into gripping contact with the end of said work piece.

9. A gripper jaw comprising a housing forming an inclosed chamber, said housing including a wall having an opening therethrough adapted to permit the axial insertion of a part to be gripped within said chamber, a mass of generally spherical, freely movable balls approximately filling said chamber'and normally loosely confined therein, said opening communicating directly with a portion of said chamber normally filled with said balls and the size of said balls being so related to the size of said chamber and of said opening that, when a part to be gripped is axially inserted through said opening it will radially displace certain of said balls and become completely imbedded in and surrounded in all radial direc tions by a plurality of layers of said balls and be directly contacted on all sides thereof by a plurality of the balls forming the innermost of said layers, and means for applying pressure to the outer portion of said mass of balls whereby force will be transmitted in all directions throughout said mass to urge the balls in the interior of said mass together so as to produce a gripping action on a part imbedded therein.

10. A gripper jaw comprising a housing forming an inclosed generally cylindrical chamber, said housing including a readily removable end wall having an opening therethrough adapted to permit the axial insertion of a part to be gripped within said chamber, a mass of generally spherical, freely movable balls approximately filling said chamber and normally loosely confined therein, said opening communicating directly with a portion of said chamber normally filled with said balls and the size of said balls being so related to the size of said chamber and of said opening that, when a part to be gripped is axially inserted through said opening it will radially displace certain of said balls and become completely imbedded in and surrounded in all radial directions by a plurality of layers of said balls and be directly contacted on all sides thereof by a plurality of the balls forming the innermost of said layers, and expansible means for applying pressure to the outer portion of said mass of balls whereby force will be transmitted in all directions throughout said mass to urge the balls in the interior of said mass together so as to produce a gripping action on a part imbedded therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,446,026 Wetmore Feb. 20, 1923 1,754,132 Van Bekkum Apr. 8, 1930 2,006,913 Conley July 2, 1935 2,469,198 La Pointe May 3, 1949 2,548,096 Bryant et al. Apr. 10, 1951 2,596,772 Hawkes May 13, 1952 2,715,532 Gunther Aug. 16, 1955 

